There's a reason all bike catalogs and web sites feature a disclaimer about parts and specifications being subject to change...manufacturers do little things like this all the time. Also, "full Ultegra" is rarely that, and it's fairly common for manufacturers to step down a notch on a cassette as it's not a super visible part and offers a marginal difference in performance.

Lastly, as has been said, it's not at all worth it for the shop to swap cassettes.